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Time of Flight Secondary Ion Mass Spectrometry


Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) is a surface characterization technique which is based upon the liberation and identification of ions that are sputtered from a sample’s surface. This method is extremely surface sensitive since most of the liberated material comes from the top-most surface layers, yet it also has the capability to selectively etch away material and perform in-depth analysis. The data provide molecular and elemental information about the sample.

With this technique, the sample surface is interrogated with a pulsed beam of high energy primary ions. As the primary ions impact the sample their energy is transferred to the surface region, and this energy is sufficient to both release and ionize local molecules and atoms. The newly-formed secondary ions are accelerated into a mass analyzer where they are separated according to their mass-to-charge ratios. The mass-to-charge ratio is used to identify the species present in the sample. Fragmentation patterns and isotope ratios aid in the identification of many species in complex matrices.

Technique Advantages

  • Imaging resolution down to 70 nm
  • Mass resolution in excess of 10,000 (m/Δm) provides molecular and elemental information
  • Depth profile analysis
  • 2D and 3D imaging capabilities
  • Dual charge neutralization allows for the analysis of electrically insulating materials
  • Minimal sample preparation for vacuum compatible materials
  • Multiple ion beams enable a broad variety of materials to be analyzed

Typical Applications for Secondary Ion Mass Spectrometry

SIMS excels at monitoring local chemical distributions in 2D across a surface and also as a function of depth. Because of these abilities, many different material systems can utilize the information provided by SIMS.

  • Biological materials
  • Organic and inorganic films
  • Polymers
  • Semiconductors and electronic materials
  • Metals
  • Instrumentation - Physical Electronics nanoTOF II
  • Bi liquid metal ion gun for analysis, may also be used to sputter-etch the sample
  • Selectable Ar or O2 sputter beams
  • Large gas-cluster beam for sample cleaning or sputtering
  • Dual charge neutralization facilitated by low energy electron and ion beams
  • Inert environment sample transfer vessel
  • Sample cooling/heating from -150 to 600°C

Sample Requirements

  • Vacuum compatible
  • Relatively flat, although surface features with vertical dimensions on the order of 10’s of microns can be accommodated.
  • Lateral dimensions can be as large as 10’s of mm.
  • Hydrated materials such as tissue samples or air sensitive materials may be introduced into the vacuum chamber through cryogenic transfer or by means of an inert atmosphere chamber. Contact the MCL staff for more information.


For more information about this instrument, visit their website: Physical Electronics